Abstract：
Endo-β-N-acetylglucosaminidases (ENGases) are enzymes that hydrolyze the N-linked oligosaccharides. Many ENGases have already been identified and characterized. However, there are still a few enzymes that have hydrolytic activity toward multibranched complex-type N-glycans on glycoproteins. In this study, one novel ENGase from Bacteroides nordii (Endo-BN) species was identified and characterized. The recombinant protein was prepared and expressed in Escherichia coli cells. This Endo-BN exhibited optimum hydrolytic activity at pH 4.0. High performance liquid chromatography (HPLC) analysis showed that Endo-BN preferred core-fucosylated complex-type N-glycans, with galactose or α2,6-linked sialic acid residues at their non-reducing ends. The hydrolytic activities of Endo-BN were also tested on different glycoproteins from high-mannose type to complex-type oligosaccharides. The reaction with human transferrin, fetuin, and α1-acid glycoprotein subsequently showed that Endo-BN is capable of releasing multi-branched complex-type N-glycans from these glycoproteins.
摘要：
内切-β-N-乙酰葡糖胺糖苷酶(ENGases)是水解N-连接寡糖的酶。许多ENGase已经被鉴定和表征。然而,仍然有一些酶对糖蛋白上的多分支复合型N-聚糖具有水解活性。在这项研究中,鉴定并表征了一种来自正地拟杆菌（Endo-BN）物种的新型ENGase。制备重组蛋白并在大肠杆菌细胞中表达。该Endo-BN在pH4.0时表现出最佳的水解活性。高效液相色谱（HPLC）分析表明，Endo-BN优选核心岩藻糖基化复合型N-聚糖，在其非还原末端具有半乳糖或α2,6-连接的唾液酸残基。还对从高甘露糖型到复合型寡糖的不同糖蛋白测试了Endo-BN的水解活性。与人类转铁蛋白的反应，fetuin,和α1-酸糖蛋白随后表明Endo-BN能够从这些糖蛋白释放多分支复合型N-聚糖。
